Lepidopteran egg parasitoids
Locally occuring parasitoids can be highly effective at suppressing pest populations, and there is a wide diversity of parasitoids that target the eggs of lepidoptera (moths and butterflies). In Australia, the order Chalcidoidea is most prominent, which includes the families Aphelinidae (Aphelinids), Chalcididae (Chalcidids), Encyrtidae (Encyrtids), and Trichogrammatidae (Trichogramma) families.
Egg parasitoids exhibit diverse physical characteristics, and appear in colours such as yellow, brown, black, and metallic shades. These tiny wasps, usually less than 1mm in length, present challenges for field observation. Instead, monitoring their presence can be done by collecting lepidoptera eggs and storing them in a transparent container, as parasitized eggs darken to black.
Depending on the parasitoid species, eggs can be laid individually or in clusters. The larvae of these parasitoids develop and pupate within moth eggs, ultimately emerging as fully formed wasps. This process results in the destruction of host eggs before hatching, effectively preventing potential crop damage.
While some parasitoid species have a narrower host range, targeting specific lepidoptera families or even individual species, others possess broader abilities to parasitize various lepidoptera hosts within a given habitat. Importantly, lepidoptera parasitoids exclusively attack and eliminate lepidoptera and do not cause harm to plants, other insects, livestock, or humans.
Parasitoids can be found in various habitats where lepidoptera are present, including greenhouse and open field crops. Adults are commonly observed at flowers or actively searching for hosts around trees, vegetation, or plant litter. They thrive in protected environments with well-developed foliage, such as crops.
Creating diverse habitats with hedgerows, cover crops, brushpiles and wildflower strips can support generalist predator population, by providing additional food sources, nesting sites, and protection from pesticide exposure or extreme weather conditions. This aids parasitoid survival during non-crop periods or when crop conditions are suboptimal, improving early season control.
Many parasitoid species are highly sensitive to these insecticides, and excessive use can be detrimental to parasitoid populations and their effectiveness as biological control agents.
Consider adopting integrated pest management (IPM) practices, which involve using pesticides judiciously and as a last resort. Targeted application of pesticides, avoiding broad-spectrum ones, and selecting insecticides that have minimal impact on non-target organisms can help preserve parasitoid populations.